The present invention relates generally to laser systems, and more specifically to a ring mirror assembly for use in laser systems to reduce mirror distortions resulting from temperature variations.
High energy laser cavities are commonly equipped with one or more ring mirrors, which reflect radiant energy into the cavity in order to further stimulate the emission of coherent radiation. It is recognized that the alignment of these mirrors is of critical importance in order to maintain maximum output.
Frequently, laser mirrors experience thermally induced misalignment after they have been initially correctly aligned. The task of reducing the effects of temperature variations on ring mirrors in high power lasers is alleviated, to some extent, by the techniques disclosed in the following U.S. patents, which are incorporated herein by reference:
U.S. Pat. No. 3,861,787 issued to Locke et al;
U.S. Pat. No. 4,121,175 issued to Kirtland et al;
U.S. Pat. No. 3,894,795 issued to Laurens; and
U.S. Pat. No. 4,370,568 issued to Lumley.
The above-cited references all disclose cooling systems which are used in high powered lasers. The patent of Locke et al discloses a laser mirror having a cooling manifold with nested, annular, cooling channels. Each of the channels has a uniform cross-section. The Laurens reference discloses a laser cavity having two concentric cooling passages for the laser window and multiple conduits.
The annular cooling channels which are normally used in the ring mirror assembly of high power laser systems has been found by experience to be subject to azimuthal temperature variations. These temperature variations extend to and include the cooling passages to produce a demonstrable temperature difference between the coolant in the inlet manifold and the coolant in the outlet manifold. Constant area manifolds, such as disclosed by Locke et al, can not produce azimuthally uniform temperatures in the ring mirror assembly, or the ring mirror itself, because the coolant will always heat up as it passes around the circumference of the manifold.
From the foregoing discussion, it is apparent that there currently remains a need for a ring mirror assembly with an inherent flow distribution design which will reduce or eliminate azimuthal temperature variations around the ring mirror. The present invention is intended to satisfy that need.